As disclosed in Japanese Examined Patent Publication JP-B2 5-83657 (1993), for example, a sinker apparatus has been conventionally used that includes, between knitting needles arranged on a needle bed in a weft knitting machine, a movable sinker displaced by a cam mechanism provided on a carriage such that the movable sinker is swingingly displaced with, as a supporting point, the vicinity on the side of a needle bed gap of the needle bed, so that the front end of the movable sinker moves forward into the needle bed gap and is withdrawn from the needle bed gap. In this case, the carriage is provided with two separate press cams. The front end of the movable sinker is swingingly displaced by an action of one press cam and moves back and forth with respect to the side of the needle bed gap in conjunction with the travel of the carriage. Thus, the movable sinker can press a knitted fabric, and can be withdrawn from the needle bed gap to prevent, for example, a mechanical contact with other components from being caused in the narrow needle bed gap. A force of a spring is also applied to the movable sinker. When a resisting force from a knitting yarn becomes greater than the force of the spring, there is room in which the front end of the movable sinker moves backward from the needle bed gap, and thus too strong a tensile force can be prevented from being applied to the knitting yarn. When the carriage moves away, a state is kept in which the movable sinker has moved forward into the needle bed gap by the force of the spring.
Furthermore, when a knitted fabric is knitted with the carriage by letting knitting needles move forward into and backward from the needle bed gap, in a case where compound needles are used as the knitting needles, the amount of the back and forth displacement can be made smaller than in a case where latch needles are used, so that a knitting cam provided on the carriage can be made smaller. In a case where compound needles are used, as disclosed in Japanese Unexamined Patent Publication JP-A 7-258946 (1995), for example, a yarn guide member whose front end is moved forward into the needle bed gap in conjunction with a knitting needle to guide a knitting yarn to a hook is used together with a movable sinker in order to reliably feed a knitting yarn to the hook at the front end of the knitting needle. As in the sinker apparatus in JP-B25-83657, the movable sinker is swingingly displaced centering about a supporting point that is supported at the vicinity on the side of the needle bed gap of the needle bed, so that the front end of the movable sinker can move back and forth with respect to the side of the needle bed gap.
The movable sinkers as disclosed in JP-B2 5-83657 and JP-A 7-258946 are swingingly displaced while supported at the vicinity on the side of the needle bed gap of the needle bed. By a cam mechanism provided on the carriage pressing a portion close to the support portion to the side of the bottom face of the needle bed, the swinging displacement is performed in which the front end of the movable sinker moves back and forth with respect to the side of the needle bed gap. On the contrary, as disclosed in Japanese Unexamined Patent Publication JP-A 5-59642 (1993), for example, a configuration is also possible in which a portion close to the support portion of the sinker that is swingingly displaced is engaged with the front end of the sinker jack that is linearly displaced forward into and backward from the needle bed gap, and the sinker is switched between an upper needle bed and a lower needle bed of a weft knitting machine with a double-deck bed.
Furthermore, in a weft knitting machine having the structure in which front and rear needle beds are opposed to each other with the needle bed gap interposed therebetween, various types of knitting is made possible by enabling a pattern with a racking and a fashioned knitted fabric, for example, to be knitted with a racking operation in which the front and rear needle beds are shifted relative to each other. However, in a case where a knitted fabric is knitted using a thick knitting yarn, when a racking operation is performed, there is a possibility of damaging by the front end of the sinker scratching a knitted fabric that is hooked on a knitting needle on the needle bed opposed thereto, and thus it is preferable that the front end of the sinker is moved backward from the needle bed gap. A movable sinker apparatus that is swingingly displaced is provided with rest retaining means for letting the movable sinker be at rest in a state where the front end is moved backward from the needle bed gap, even after the carriage has passed, as disclosed in Japanese Unexamined Patent Publication JP-A 9-31806 (1997). The rest retaining means is achieved as a sinker rest retaining plate that moves forward into and backward from the needle bed gap linearly and in parallel with a knitting needle. When the sinker rest retaining plate is partially brought into contact with a movable sinker, the front end of the movable sinker is held in a state moved backward from the needle bed gap.
With the sinker apparatus in JP-B2 5-83657 and JP-A 9-31806, it is necessary that a cam mechanism for swingingly displacing the movable cam and for pressing the movable cam during a stitch determination is provided on the side of the carriage. Accordingly, the carriage has to cover the surface of the needle bed up to the range that is close to the needle bed gap, and thus a wide space cannot be secured at the needle bed close to the needle bed gap, which is an area for knitting a knitted fabric.
Furthermore, in order to increase the amount in which the front end of the movable sinker is displaced on the side of the needle bed gap, it is necessary to shorten the distance from the support portion of the movable sinker to the drive portion with respect to the distance from the support portion to the front end. In the configuration in which the movable sinker is swingingly displaced with a pressure from the carriage to the side of the bottom face of the needle bed as in JP-B2 5-83657 and JP-A 7-258946, it is necessary that a mechanism such as a press cam is provided on the side of the needle bed gap of the needle bed. Thus, the carriage is formed so as to cover the needle bed up to the vicinity of the needle bed gap, and thus becomes large.
In the most commonly used type of weft knitting machine, a pair of needle beds of the front and the rear face each other in the shape of a mountain with a needle bed gap interposed there between such that the needle beds become lower as being away from the needle bed gap. Thus, in the vicinity of the needle bed gap, which is an area for knitting a knitted fabric, the front and rear needle beds are close to each other and thus the space between the needle beds is narrow. In addition, it is necessary to provide a plurality of yarn feeders for feeding a knitting yarn and other components in this space. Accordingly, in order to make the weft knitting machine smaller and in order to make it possible to knit various types of knitted fabrics, it is necessary to secure a wide space in the vicinity of the needle bed gap.
Furthermore, in the movable sinker as in JP-B2 5-83657, a knitted fabric is pressed by a force of a spring, and when a resisting force of a knitting yarn becomes greater than the force of the spring, the movable sinker moves backward from the needle bed gap, and thus a tensile force applied to the knitting yarn can be relaxed, so that it is possible to prevent too strong a tensile force from being generated. However, it is necessary that the carriage is provided with a mechanism for pressing the vicinity of the support potion of the movable sinker, such that the movable sinker is swingingly displaced in the vicinity on the side of the needle bed gap of the needle bed, and thus the carriage has to cover the needle bed up to the vicinity on the side of the needle bed gap.
Furthermore, the sinker in JP-A 5-59642, a sinker that is swingingly displaced is shared between an upper needle bed and a lower needle bed of a double-deck bed, and the sinker is remotely driven via the sinker jack at the position away from the needle bed gap such that the sinker is operated for knitting a knitted fabric on either one of the needle beds. Thus, it is not necessary to provide, for example, a press mechanism for letting the sinker operate in the vicinity of the needle bed gap. The sinker is swingingly displaced in order to switch the operation object between the upper needle bed and the lower needle bed, and thus the sinker always acts on the knitted fabric that is knitted in either one of the needle beds. Furthermore, a force applied from the cam of the carriage to the sinker jack is transmitted, via the sinker that is swingingly displaced, to the knitting yarn, and there is no space in which the sinker can move backward from the needle bed gap even when a resisting force from the knitting yarn is received, and thus there is a possibility that too strong a tensile force is generated in the knitting yarn.